In U.S. Pat. Nos. 5,896,713 and 6,035,593, both of which are owned by the same assignee as is the present invention and both of which are incorporated herein by reference, tubular skylights are disclosed. Both of the skylights can use the skylight dome disclosed in U.S. Pat. No. 5,896,712 also owned by the same assignee as is the present invention and also incorporated herein by reference. These inventions represent advances over the prior art and one or more of them has found commercial success.
Briefly, a tubular skylight such as those mentioned above includes a tube assembly mounted between the roof and ceiling of a building. The top end of the tube assembly is covered by a roof-mounted dome or cover, such as the one disclosed in the above-mentioned '712 patent, while the bottom end of the tube assembly is covered by a ceiling-mounted diffuser plate. With this combination, natural light external to the building is directed through the tube assembly into the interior of the building to illuminate the interior.
Tubular skylights use a reflective surface to transport sunlight down a tube from the roof to the interior ceiling. The optical spectral response of the dome, tube, and diffuser and the number of light reflections as light travels down the tube determines how much sunlight will reach the interior of the building. These properties will also determine how much heat, in addition to visible light, will be transported to the interior.
As recognized herein, it is desirable to maximize the amount of visible light (light having wavelengths of between around four hundred nanometers and seven sixty nanometers) that is transmitted down the tube while minimizing the amount of heat (in the form of infrared light of greater than around seven hundred sixty nanometers) that is transmitted into the room. As further recognized herein, most fenestration products designed to minimize solar heat gain unfortunately have drawbacks. For example, tinting the surface of a window with a coating or film typically is not selective, i.e., tinting reduces heat transmission but also reduces visible light transmission. The same is true to a somewhat lesser degree with respect to low-e coatings and/or films that are deposited on windows as well as with respect to multiple glazing layers. Furthermore, the same observations apply to skylights, in which films or coatings that are used to maximize visible light transmission down the tube also maximize heat input into the room and in which optical blocking devices in the dome or diffuser, while blocking IR, also block visible light. Accordingly, the present solutions are provided.